Yang, Hsun-An , Chung, Kuo-Fang , Leong, Wai-Chao , Peng, Ching-I .
The Origins of Taiwanese Begonias.
Taiwanese begonias have a notably high level of endemism (over 70%) relative to other taxa. Of the 18 named species, four are confirmed natural hybrids. Based on morphology of ovary and placenta, the remaining 14 species are classified into three sections, including sect. Diploclinium, sect. Platycentrum, and sect. Sphenanthera. However, previous cytogenetic studies found that karyomorphological evidence does not support present classification. Furthermore, rather than a common chromosome number of 2n=22 and 2n=30 reported from adjacent regions(e.g. China), surprisingly diversified chromosome numbers (2n=22, 26, 36, 38, 52, 60, 64, 82) are found in Taiwanese begonias. These remarkably figures indicate that allopolyploidization events followed by aneuploidization might have played an important role in the diversification of Taiwanese species. In order to reveal the origins and speciation history of Taiwanese begonias, DNA sequences of low-copy nuclear genes (PI, TFL, RPB2) and cpDNA spacers (trnL-trnF, trnC-ycf6, accD-psaI, ndhF-rpl32) of Taiwanese and representative begonias from adjacent regions were analyzed. The nuclear gene trees and cpDNA trees all support that B. ravenii (Sect. Diploclinium) and B. fenicis (Sect. Diploclinium) are two distinct species and belong to different clades of Sect. Diploclinium. In PI gene tree, other Taiwanese begonias and species of Sect. Sphenanthera form a group sister to Sect. Platycentrum, suggesting those Taiwanese species in Sect. Diploclinium might have originated from hybridization between Sect. Sphenanthera and Sect. Platycentrum. In addition, B. longifolia (Sect. Sphenanthera), a species widely distributed in East and Southeast Asia, seems to directly involve in the formation of the species diversity in Taiwan. Furthermore, multiple copies from polyploidy species are separately found in different clades, suggesting allopolyploid origins of Taiwanese begonias.
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1 - National Taiwan University, School of Forestry and Resource Conservation, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
2 - Academia Sinica, Research Center for Biodiversity, 128, Sec 2, Academia Rd., Nangang, Taipei, 115, Taiwan
low-copy nuclear gene.
Presentation Type: Poster:Posters for Sections
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM